[SunkenCiv]

This article reiterates the 'rubble pile' explanation, but notes that one end is lower density than the other. That could be suggestive of water ice. My view is that all the Earth-crossers formerly were part of now-extinct comets.

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KEYWORDS: asteroid; asteroiditokawa; hayabusa; itokawa

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[Chode]

that's a valid explanation

[Telepathic Intruder]

That’s interesting, actually. Then they’re constantly being replenished even with the occasional Tunguska event. There’s just a tiny whisper of gravity holding asteroids together, however. Low density does not necessarily imply light elements.

[Swordmaker]

This article reiterates the 'rubble pile' explanation, but notes that one end is lower density than the other. That could be suggestive of water ice. My view is that all the Earth-crossers formerly were part of now-extinct comets.

Unfortunately for your theory, every comet we've analyzed or visited has shown essentially zero water. . . and is indistinguishable from any other asteroid except for orbit and electrical charge.